Techniques are known which provide geo-localization of a user equipment (UE) in a mobile communications network. The UE is typically portable and establishes data communication with an access node of the mobile communications network via a radio link. Therefore, the UE typically exhibits a time-varying position which needs to be determined from time to time.
The position of the UE is often defined with respect to a location and/or an altitude. The location can be defined as, e.g., geographical latitude and longitude. The altitude can be defined as, e.g., elevation with respect to sea level or elevation with respect to a reference coordinate system or a geoid, e.g., as specified by the World Geodetic System (WGS) 1984, or elevation with respect to any other reference altitude.
Various techniques are known which allow determining the location and altitude. For example, positioning by means of one or more Global Navigation Satellite Systems (GNSSs) is known. GNSSs include the Global Positioning System (GPS) and the Galileo System. A further technique of determining the position of the UE is the Observed Time Difference of Arrival (OTDOA) method. This method utilizes the differences of time measurements of downlink radio signals from a plurality of access nodes of the mobile communications network, e.g., along with knowledge of the location of the access nodes and/or their relative downlink timing. Yet a further technique of determining the position of the UE is a so-called cell identification positioning technique. Here reference signals transmitted via the radio link of the mobile communications network can be employed together with knowledge of the location of a respective access node.
Yet, such techniques face certain restrictions. Typically, an accuracy when determining the altitude of the UE is limited; in particular, error margins for the determined altitude may be significantly larger than for the determined location. For example, the accuracy of the determined altitude may be in the order of tens of meters or more—while, in comparison, the accuracy of the determined location may be in the order of one or two meters. Such limited accuracies of the determined altitude can be insufficient for various applications, including, but not limited to floor-level navigation in a high-rise building.
In this regard, it is known to perform barometric pressure measurements at the UE, e.g., from EP 1 154 231 A1 and US 2002 090 976 A1. Barometric calibration data is provided by an access node to the UE. Based on the barometric calibration data, the UE can determine its altitude, preferably with a higher accuracy.
Yet, also these techniques face certain restrictions. Due to the large number of UEs, scenarios can occur where the work-load imposed on the access node is comparably high. Further, it may be necessary to perform reference measurements, e.g., at an access node, and/or to access an external database in order to provide the barometric calibration data. E.g., the reference measurements may be subject to failure, offsets, and generally may need to be supervised. As a further example, the access to an external database, e.g., from a weather data provider, may be subject to failure as well. Further, the data of the database may be limited in accuracy. All this may increase system complexity and a likelihood of system failure.
Accordingly, there is a need for techniques which allow for providing advanced techniques for determining the altitude of a UE. In particular, a need exists for such techniques which allow for an accurate determining of the altitude. Furthermore, a need exists for such techniques which allow determining the altitude with limited computational resources. Furthermore, a need exists for such techniques with limited system complexity and low likelihood of system failure.